2009-06-08

Spirit Sol 153

We're just 170m from the hills now -- and I'm on shift for the next four sols, so we might just reach them on my watch. Of course, lately we've been regularly making 90 or 100m in a single sol, so that might not seem to be a problem. But now that we're closer to the hills, the terrain is getting rougher again, so we'll make less progress per sol, making this something of a race.

We've reached Plymouth Rock, a rock about 50cm tall and 1m wide, which has been our aim point for the last several weeks. One of our PANCAM images happened to capture it perfectly. Fortunately, it's off to our right; today's drive will have to go only about 1m out of its way to skirt this monster rock.

I'm early, but I try to make myself useful as soon as I arrive. Eavesdropping on the intense activity planning discussion in the corner, I gather they're trying desperately to save a few minutes in the plan, and are thinking about cutting the end-of-drive stutter step.

"What if we drop the stutter step and unconditionally dump the HAFIQ?" I suggest. This gives us a set of low-resolution pictures leading up to the final position (or so we hope; autonav may aim the rover in the wrong direction for our purposes, making this something of a gamble) without the overhead normally associated with our end-drive imaging. This saves about five minutes, which turns out to be enough to be useful. (Indeed, better than merely useful, it turns out to be enough to save a science observation. Jeff Norris says, only half joking, "Some grad student writing his thesis six years from now will be very happy we took this PANCAM image.")

As has been usual of late, we're running well ahead of schedule -- nearly an hour ahead. But scientists are going to be participating remotely -- that is, calling in -- starting soon, and that doesn't work if the meetings start early. So John and I hand over early, and for the first time in some weeks, I handle the activity plan approval meeting when it happens.

This drive sequence is r0101 -- our 101st drive sequence. (Or thereabouts -- for some now-forgotten reason we didn't have a r0000 or r0001, but we have some drive sequences with other wacky numbers.) "Annoyingly," John says, "Opportunity has more drive sequences than we do, even though they've done less driving." This is because they split the drive sequences more often than we do, inflating their number. As of today, they're on r0102.

And incidentally, their r0102 has a scary description: "position_for_entry." This is, of course, their entry into Endurance Crater, which they've officially decided to go for. Cooper told me the other day he was hoping they wouldn't do this -- there's a lot of interesting stuff outside the crater they could go look at instead. One of the ideas floating around was to drive Opportunity to its own heatshield and RAT it. This would be the first time we'd ever done that kind of investigation into what happens to a spacecraft landing on another planet, and could teach us lessons we could use to make future landers lighter and more reliable. But if Opportunity gets stuck in Endurance Crater, that option is foreclosed.

With all the obstacles in our way, we're not sure how far we'll be from the hills following thisol's drive. We know we'll go about 40m closer, but after that it's up to autonav's ability to take us through this more difficult terrain. When one of the scientists asks, Julie says, "We'll be 100m from the hills if autonav does its job."

"Autonav's number one job is to keep the rover safe," I point out. "Moving you closer to the target is job number two."[1]

So however far we get thisol, we'll get another shot at the hills tomorrow. If autonav does its job, and we do ours.